Bedroom

Utilize a straight edge and your sense of feel to tape everything you do not want painted. 

Cover the floor, doors, and windows in plastic, make sure it will stay put by using tape (not duct tape). You might splatter and you might not see it. 

Don't overload your brush or roller and go slowly and steadily until you're comfortable with it. Work methodically!

Wall paper tells you exactly how far the pattern is. If you don't have access to the digital version of the label, see if you can use an enlarger or ask for help. Use a blind-friendly measuring tape, and make cuts based on math. I'm serious. If the pattern is 54cm, and your wall is 230cm, you know you will be 26cm into the next pattern. Just use math!

The glue doesn't dry quickly. Work methodically and make sure everything has an even coat. Do not be in a hurry and slop glue everywhere.

There are smoothing rollers to help get the bubbles out. You won't see the bubbles probably but you can feel them, try to make sure you work from the center out.